Spring contact



Jan. 16, 1940. F, FORSMAN 2,187,023

SPRING CONTACT Filed Sept. 10, 193? FIG. 2

INVENTOR. FRED FORSMAN ATTORNEY.

Patented Jan. 16, 1940 V UNITED STATES SPRING CONTACT Fred Foreman, Chicago, Ill., assignor to Teletype Corporation, Chicago, Ill., a corporation of Delaware Application September 10,1937, Serial No. 163,193

3 Claims.

The present invention relates to contact springs l and particularly flat metallic spring elements which are flexible into contactual engagement with adjacent, contactors for the establishment of 6 electrical circuits.

Flat metallic contact members parallelly arranged and supported upon insulating material are secured at one end and their free ends are flexed so that contact points carried usually at 10 a short distance from the free ends may be made to effect electrical and contactual engagement with each other. The present invention concerns a novel construction and manner of securement of the contact points to said flexible contact elements or blades.

The main object of the present invention is to provide a sheathing for vibratory contact elements obtained from contact material economically cut, shaped, and applied under low cost methods of assembling, but a'ffording, nevertheless, rugged and efllcient operating equipment.

According to a present practice, contacting elements are soldered in position on the surface of a flexible blade, but under certain operating conditions it has been found that as a result of localized heating effects the temperature of the contact point and material to which it is attached may be raised sufliciently to melt the solder and cause a slipping, and in some cases a total dropping oil of the contact points from the surface of their supporting blades.

The present invention proposes to employ contact elements cut from stock copper tubing or other suitable 'material partially shaped and thereafter slipped into position upon flat metallic contact blades. These contact elements constitute the abutments or lugs which engage each other or which engage with specially shaped cooperating contacts. The contact lugs herewith 40 proposed comprise sheathing for their respective blades which may be held in position merely by being collapsed and pressed so as to efiect an adequate binding and adhesion or they mayi be further secured by the application of minute quantities of solder to insure against lateral displacement and also to secure additionally, conductivity through the principal contact blade. The application of minute quantities of solder in accordance with the proposed construction affords a somewhat higher degree of structural security, but together with the annular or sheathing type of contact element which permits electrical current to be conducted around rather than through the solder deposits, there is abolished a the characteristic tendencies of localized heating sometimes encountered in other types of surface adhering contact structures. s

In the following detailed specification, the manner of practicing the present invention is set forth in particular detail, reference being had 8 to the accompanying drawing in which like identification characters designate corresponding parts, and in which:

Fig. 1 is a detailed perspective view of a double acting contact spring assembly having embodied 10 therein the essentials of the present invention;

bly featured in Fig. 4 after the final crimping has been completed;

Fig. 6 is an elevational view of a modified form of contact and blade assembly in which the edges are crimped and made to conform with recesses 25 provided edgewlse oi the principal blade;

Fig. 7 is a bracketed sectional view of a modifled embodiment of the present invention illustrating the original stock shaped in the manner of Fig. 2; 4

Fig. 8 is a cross-sectional view of the embodiment featured in Fig. '7 after. the iih'al crimping and the other assembly processes have been completed;

Fig. 9.15 a sectional view of an additional modi- 35 flcation more nearly related to that of Figs. 7 and 8 after assembly, but indicating the use of a channel instead of tubing for providing the material from which the contact sheathing is formed; and

Fig. 10 is a side elevation of a contact arrangement in which the features of the present inven-' tion are carried over into the design and equipment of the inert contach elements, as well as that of the intermediate flexure member.

Spring blades such as the one illustrated by the numeral Ii, Fig. 1, are usually made of a metal or alloy whose prime quality is its elasticity, but whose other characteristics are sometimes quite disadvantageous. Notable among inciden- 5o tal but undesirable features thus encountered in elastic metal alloy are low conductivity and relatively high oxidation or corrosion. In contact assemblies such as are employed in the art of printing telegraphy, a contact element is fre: 5g

quently subjected to severe strains attributable largely to the frequency of its flexure vibrations, and unless the natural qualities of its metal are capable of withstanding service under these conditions, frequent breakage occurs.

Flexible metals usually are not suitable for the maintenance of a sufiiciently clean surface contact to promote instantaneous electrical conductivity upon contactual engagement between adjacent contact springs I2 and I3, and in order to obtain the advantages both of adequate resiliency and flexibility and clean contact engagement, the contiguous surfaces of the vibrating contact blade are customarily tipped with noneorroslve metals suitable for this purpose. Thus in Fig. 1, while the contact spring II may be made of nickel steel or any other metal having the proper spring temper to withstand the strains of frequent flexure and vibration, the contact elements I2 and I3 are preferably constructed in the form of laminiferous leaves usually made of phosphor bronze and turned inwardly, as at M, so

, as to impart a slight abrasive wiping action at original appearance.

their point of engagement with the flexure blade II. A metallic overlay E5 is secured upon the blade I I at the point whereat the inwardly turned sections it are adapted to engage it. Portion I5 is preferably made, of a corrosion and oxidation resisting conductive metal such as copper, and it is preferably of adequate size to cover a range of area somewhat greater than the area of blade II engaged by the ends of the contact members l2 and I3.

The flexing of blade II is stimulated mechanically by a force applied at its end and for this purpose the blocks of insulation I6 are provided, while at the rigid end suitable insulating material IT constitutes part of the securing and spacing means. In the construction of blade I land particularly in the application thereto of metallic contact overlay portions I5, 2, length of flem'ble metal A is out to form the blade while from a stock of copper tubing an annular ringlet B of suitable length is severed. Fig. 2 illustrates the relative size of the two portions of stock in their The ringlet B is flattened to the approximate shape, illustrated. in'Fig. 3, it being of suitable proportions so that its internal cross-sectional space 2|, when flattened as in Fig. 3, is just large enough to receive the flexure member II as indicated in Fig. 4.

The space 2| should preferably be just large,

enough to receive snugly blade II without permitting any appreciable side play or wobble. The ringlet B is moved into the proper position longitudinally upon the blade II and thereat pressed into the shape illustrated in Fig. 5 with the curved ends crimped down as at 22 so as to remove all surplus space. This assembly has been found to afford adequate adhesion to resist any tendency at longitudinal displacement imparted to the contact rlnglet I5 by the inwardly turned portions I4 during the wiping engagement therewith. However, as an additional precaution, a small quantity of solder may be introduced in order to join the two materials more securely. Even where solder is employed for this purpose, however, its

function may be relied upon as an auxiliary and not as a sole adhesion supporting medium so that under temperatures sufficient to liquefy the solder, the normal adhesion properties m ay be dey of an annular ring for the purpose of effecting contact engagement, it is noteworthy that a larger area is thereby afiorded for electrical conductivity between the contacting member I5 and blade II, contributing thereby towards a minimum of local heating tendencies which might arise due to intermediate resistance between the two members.

Modifications In Fig. 6 there is illustrated a method for further securing the annular ring I5 against longitudinal displacement on the blade II by pro viding the notches 26 upon the opposite edges of the blade II and thereafter by crimping the edges as at 22 and in addition thereto, of pinchmg the recesses 21 to conform with the aforementioned notches 26.

Instead of the annular tubing section B described above, one C with a longitudinal seam 23, Fig. 7, may be employed having the special advantage of perimetric adjustment to conform with the outline of a variety of cross sections of the element A. A conventional assembly is illustrated in Fig. 8 showing in general the appearance of one adaptation of this modification, but where any special shapes or proportioning of the flexible element A are contemplated, it will be seen that the longitudinal seam 23 affords a means of contraction and expansion to the memberC whereby special forming processes are obviated and also whereby conformation to irregular contours is more easily obtained.

There is illustrated a further modification in Fig. 9 Where instead of an annular strip C a. channel D is cut off to the proper length and folded over as indicated by the dotted outline 28. This assembly may be recognized as resembling that of Figs. '7 and 8. However, by employing channel material instead of cylindrical stock the preliminary shaping process may be entirely eliminated. Obviously, in either type,

. Figs. 7 or 9, the seam may be arranged to be located at other places in the periphery of the material II from that illustrated.

In Fig. 10 there is illustrated a contact pile-up in the contacting region of which all of the components may be equipped, in the manner illustrated in Fig. 1 for the blade u solely. This shows also that as a further feature of the present structure, any number of adjacent contact members are, by the single installation, provided with double acting capacities.

In the accompanying drawing and in the foregoing specification, certain embodiments are featured, but it will be understood that numerous variations therefrom may be made within the spirit of the present invention. It is, therefore, intended not to be limited in any particular to the details herewith disclosed except as indicated by the following claims.

What is claimed is:

i. In an electrical contact assembly, a flexible 2. A contact element comprising a blade oi flexible metal, a. relatively rigid contact member, means for securing one end of said blade and one end of said member stationarily and in electri- 8. In a contact assembly. a plurality of flexible blades secured together at one end in parallel, spaced, superposed and electrically isolated relation, a contactor carried by each of said blades in superposed alignment in the proximity of the free-ends of said blades, said contactors comprising ringlets of highly conductive material collapsed into loose enc'irclement of said blades and thereafter pressed into binding engagement therewith and thrust receiving means carried by one oi said blades at the free end thereof whereby said blade may be flexed to bring the contactor thereof into engagement with the contactor of another of said blades.

FRED FORSMAN. 

